[TCML] DRSSTC weird waveform behavior
tkoivuro at gmail.com
Sat Jul 2 05:36:49 MDT 2011
Justin forgot to mention that he has gate resistors bypassed by UF
diodes so his effective turn-on resistance is 10ohms and turn-off
resistance is 0ohms. Phase lead feedback is good idea but still you
dont need blistering fast switching speed.
V = L * dI/dt should explain why slowing down is good idea. I have
CM300 drsstc engine and i run my gates at little over 1µs rise time at
60kHz. It has been tested up to 1800Apk without any troubles. After
crude phase lead adjustment i still had some overshoot at gates and
inverter output + some common mode noise issues. All that went away
when i reduced switching speed by factor of 3 or something like that.
My current way to determine "good enough" switching speed is to slow
it down untill switching losses become problem and and then speed it
up just a little bit.
These large power bricks have pretty large internal inductance too
(easily 50-100nH) and there is nothing you can do about it. Switching
too fast may excite these inductances in resonance with dc bus
Just my 0.02euros
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